In the course of treating and preparing subterranean wells for production, a well packer is run into the well on a work string or a production tubing. The purpose of the packer is to support production tubing and other completion equipment such as a screen adjacent to a producing formation and to seal the annulus between the outside of the production tubing and the inside of the well casing to block movement of fluids through the annulus past the packer location. The packer is provided with anchor slips having opposed camming surfaces which cooperate with complementary opposed wedging surfaces, whereby the anchor slips are radially extendible into gripping engagement against the well casing bore in response to relative axial movement of the wedging surfaces. The packer also carries annular seal elements which are expandable radially into sealing engagement against the bore of the well casing in response to axial compression forces. Longitudinal movement of the packer components which set the anchor slips and the sealing elements may be produced either hydraulically or mechanically.
After the packer has been set and sealed against the well casing bore, it should maintain sealing engagement upon removal of the hydraulic or mechanical setting force. Moreover, it is essential that the packer remain locked in its set and sealed configuration while withstanding hydraulic pressures applied externally or internally from the formation and/or manipulation of the tubing string and service tools without unsetting the packer or interrupting the seal. This is made more difficult in deep wells in which the packer and its components are subjected to high downhole temperatures, for example, as high as 600 degrees F., and high downhole pressures, for example, 5,000 psi. Moreover, the packer should be able to withstand variation of externally applied hydraulic pressures at levels up to as much as 10,000 psi in both directions, and still be retrievable after exposure for long periods, for example, from 10 to 15 years or more. After such long periods of extended service under extreme pressure and temperature conditions, it is desirable that the packer be retrievable from the well by appropriate manipulation of the tubing string to cause the packer to be released and unsealed from the well bore, with the anchor slips and seal elements being retracted sufficiently to avoid seizure against well bore restrictions that are smaller than the retracted seal assembly, for example, at a makeup union, collar union, nipple or the like.